Use of detergent extracts of Brucella abortus RB51 to detect serologic responses in RB51-vaccinated cattle

Serologic responses to the newly introduced rough Brucella abortus vaccine strain RB51 have been determined in a dot-blot format using gamma -irradiat ed RB51 cells as the antigen. Because gamma -irradiated cells are not easil y prepared and the signal from cells was not always reliable, an alternativ e antigen was sought. Detergent extracts of B. abortus RB51 were prepared u sing zwittergent 3-14, Triton X-100, and sodium dodecyl sulfate (SDS) and e xamined in a dot-blot format. Zwittergent 3-14 extracts and gamma -irradiat ed RB51 cells gave the same titers. Unlike gamma -irradiated RB51 cells, zw ittergent 3-14 extracts produced signals consistently, and the signals were easily interpreted. Triton X-100 extracts interfered with signal developme nt, and SDS extracts resulted in a high background signal. Western blot ana lyses revealed several outer membrane proteins in the zwittergent 3-14 extr act. The major antigens in the extract had apparent molecular weights of < 20,000.